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Fri, 7 Jun 2024 12:01:11 +0800 Message-ID: <4f7bcb28-bcad-4f1b-aa97-03a6b6c2fbba@huawei.com> Date: Fri, 7 Jun 2024 12:01:10 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 4/6] mm: migrate: support poisoned recover from migrate folio To: Jane Chu , , References: <20240603092439.3360652-1-wangkefeng.wang@huawei.com> <20240603092439.3360652-5-wangkefeng.wang@huawei.com> <0290a474-39f4-4549-9fc8-06ccd6321d5d@oracle.com> Content-Language: en-US From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Queue-Id: 3E592180018 X-Stat-Signature: pcfqmf6u6de5oxxoc8t6mq4eqjasqj4d X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1717732874-826282 X-HE-Meta: U2FsdGVkX18dpssLGw9Ze4urfjbnAQmxOf12kawMSAOr9BvZndMV06l1ESgfVnoRTs1190fx/5G5tY1gk7sChBTr1tMp/s2oUlUG1k8xcdYxyHCliEK007oNVjh/TWKaplBF8+NcGERJrWIOxECUp05aC7HWHliOU6rzNGnGek0TkgO0acpzhcshRVFS6WBmnFaNhDSpEDJdFFx3YxSESlcYW9JUJx3+gJHPEDc+s6dVg+cwo0S0HeFWBqGPOLdXasEMUG0LsxU+WkrOnR5W2fpk6RO2AhB6zQDZWSGrhIZY4rojaumiSVSwS/aijN98uwLkLL5Gnq6quLfim1EmBiAJRSrR/4DbOzCoC6XXYicVjt3FhNoCvQ1EcLoEi5SQirUQZxlorve3V8gzsAilJNtyRKsEYEPTq440LKKK2MaS/rYeWxuBwpLxuzyelH6sB/2bq2pKskD9Mh+cJPcEbaACE6f9oCS4ncBX/G9aiL4fpbf0VZWFm5PRU5Iav6E0HcC1YIdJeEGBf23jSAmedhZJ1/IgAnttgU3zDc+kXY4/gK2rnch3cp0BOIbwL8qJnQcuBBBUjE9E0BHe7sBNgi+HpjtVHdQmWS63/q1BiFxjbnJgQn2pnq1Glc7TjAxW5cJv8Gg2wo/gRfo+1jNjSN397fMJHGQLu1ROiYZWRkNNvmsoZ+Q1ZofGn5DRQDmnLmemtgz9ijqayhR1wpDM9TYuzGlLBJ3QR2fHHjkG+C2PpkhXxSD5tCea9gX/l8ZtLHP4wC0BHYlUFGmJtM3UeV2IpEV0qxBx3QToTezn8jerJV7zAc2mfFbvhho+4kk6sDCyXdsw0QukjArxEZpod/TilCYicvhh3GR70YfFY4vCvUcLACD9EQ914B2rPKy887VOhcnmF6luZA9GHJC270xENuI//hqJGQRSAU1faXDDvbttI5WHTd/J59pMGY3athDhxOmshRv4aMoSiAq Amdup6NH gOsCfheNdv9oHSPF0qKp5iHZJfLu5J2paMMsSi8/g5c/xWHiH/95Cj18YWqvYzAWNSYJrL3b4ragELgF48iUvuwLr30JMgYyukn8yEJGDtPvJkP/+ortw9hCYi2ePpRIa+AjTjpEOjwCuDYcDX2Obwj4FiPPqeloh9cXYUmVL5tX3kyKgEegrnOmZ2BN6ZpyFYSQ8 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024/6/7 6:31, Jane Chu wrote: > > On 6/6/2024 3:28 PM, Jane Chu wrote: >> On 6/6/2024 2:27 PM, Jane Chu wrote: >> >>> On 6/3/2024 2:24 AM, Kefeng Wang wrote: >>>> diff --git a/mm/migrate.c b/mm/migrate.c >>>> index e930376c261a..28aa9da95781 100644 >>>> --- a/mm/migrate.c >>>> +++ b/mm/migrate.c >>>> @@ -663,16 +663,29 @@ static int __migrate_folio(struct >>>> address_space *mapping, struct folio *dst, >>>>                  struct folio *src, void *src_private, >>>>                  enum migrate_mode mode) >>>>   { >>>> -    int rc; >>>> +    int ret, expected_cnt = folio_expected_refs(mapping, src); >>>>   -    rc = folio_migrate_mapping(mapping, dst, src, 0); >>>> -    if (rc != MIGRATEPAGE_SUCCESS) >>>> -        return rc; >>>> +    if (!mapping) { >>>> +        if (folio_ref_count(src) != expected_cnt) >>>> +            return -EAGAIN; >>>> +    } else { >>>> +        if (!folio_ref_freeze(src, expected_cnt)) >>>> +            return -EAGAIN; >>>> +    } >>>> + >>> >>> Let me take a guess, the reason you split up folio_migrate_copy() is >>> that >>> >>> folio_mc_copy() should be done before the 'src' folio's ->flags is >>> changed, right? >>> >>> Is there any other reason?  Could you add a comment please? >> >> I see, both the clearing of the 'dirty' bit in the source folio, and >> the xas_store of the >> >> new folio to the mapping, these need to be done after folio_mc_copy >> considering in the Yes, many metadata are changed, and also some statistic(lruvec_state), so we have to move folio_copy() ahead. >> >> event of UE, memory_failure() is called to handle the poison in the >> source page. >> >> That said, since the poisoned page was queued up and handling is >> asynchronous, so in >> >> theory, there is an extremely unlikely chance that memory_failure() is >> invoked after >> >> folio_migrate_mapping(), do you think things would still be cool? > > Hmm, perhaps after xas_store, the source folio->mapping should be set to > NULL. When the folio_mc_copy() return -EHWPOISON, we never call folio_migrate_mapping(), the source folio is not changed, so it should be safe to handle the source folio by a asynchronous memory_failure(), maybe I'm missing something? PS: we test it via error injection to dimm and then soft offline memory. Thanks.